Former US Navy SEAL Richard "Mack" Machowicz, best known for starring in the hit show "Future Weapons" on Discovery Channel, died on Monday after a long battle with brain cancer. He was 51.

The news of Machowicz' death was first shared by his friend and fellow SEAL Craig Sawyer. The website SOFREP, run by fellow SEAL Brandon Webb, also wrote of Machowicz and offered a tribute to his "nearly fifty-two years of living by example."

Machowicz had been diagnosed with Stage 4 brain cancer some time in late 2015, according to his company's Facebook page, NDCQ, or "Not Dead, Can't Quit."

"I refuse to give up on myself and what I'm capable of doing," he said in February 2016.

Though he was best known for "Future Weapons," Machowicz also hosted Spike TV's "Deadliest Warrior" and other shows on The History Channel and the Military Channel. He also authored a best-selling book, was an accomplished martial artist, and served as a Navy SEAL for ten years.

"His private messages and phone conversations have remained strong and inspiring throughout," his friend, Navy SEAL Craig Sawyer, posted on Facebook. "An amazing man in so many ways... His strength of character and integrity were outstanding."

He is survived by his wife and two young daughters.

Machowicz' company NDCQ did not respond to a request for comment from Business Insider.